Same as Simone's proffer.
The support of caldav access to calendars would really be a plus as it would give the chance to maintain the Toodledo stuff on iCal (as desktop application) as well.
Recently, this feature was successfully implemented by Google for the Google agendas. And this was possible thanks to Leopard OS X.5 which supports Caldav natively.
At the end of the day, Toodledo on the web, Toodledo lite on a networked iPhone (or any), Todo on an offline iPhone and iCal on a Mac desktop. Wow, wow ! That's worth thinking on.

Can I vote 10 times? That's just two in binary :-) I'd put both of them towards a native iPhone app! The iPhone web interface and availability of Appigo's Todo app (which I have not yet purchased due to lack of subtasks and contexts, and now I hear recurring tasks support) were two huge sellers on going to Toodledo and I recently purchased a Pro account as I like it that much.

A bonus vote would go towards Gears for offline use (would be great as a Chrome Application like I already use it, since Gears comes built into Google Chrome). But I wouldn't ask for any time to be spent on this until an iPhone app was out!

These two features would give users many more options for how to access their tasks, and might actually reduce the number of other apps & devices you get asked to provide support for.

Separate iCal links for different views would allow us to use them in apps that support iCal but don't offer any way of viewing by folder/context or don't have good sorting features (where the hotlist would provide a handy way to focus in on important tasks & ignore the "clutter").

IMAP support would give us a way to access tasks offline, without having to use Google Gears, and would also provide a way to view tasks on any device with IMAP capabilities (which will include many devices which don't currently have a way to satisfactorily view Toodledo tasks). For an example of another implementation of a non-email use of IMAP, see Evernote (http://www.evernote.com/about/support/imap.php).

I second the Evernote request. At least as far as the ability to convert tasks to evernotes (can already be done by emailing, but they then need to be processed in evernote, to move to correct notebook , and tag), and the ability to create todo's from evernotes! this is currently difficult because emailed evernotes contain html wrappers that make the note contents difficult to read.

Aside from this basic function, I'm sure there are a lot of wonder things that could be added Evernotes new service API

Could you get in touch with Evernote, and let them know you have mutual customers that would like to see some integration?